1. Field of the Invention
The invention relates to a drive device for a means of transportation, particularly a trolley bus or rail vehicle.
2. Description of Related Technology
Drive devices for means of transportation, i.e., vehicles, such as trolley buses or rail vehicles, may include an electrical connection device that can be connected to an external electrical power source. The connection device is also connected to a (static) power converter. Such a drive device may further include: a first drive aggregate in the form of an electrical drive motor connected to the power converter; a second drive aggregate in the form of an internal combustion engine; a generator connectable to the internal combustion engine and alternatively connectable via the power converter to the electrical drive motor; and at least one auxiliary aggregate for the vehicle.
Such drive devices are being used in buses, especially in trolley buses or double-decker buses. However, they could also be used in rail vehicles. Such drive devices have the advantage that, in normal operation, the driving of the vehicle is performed via the electrical drive motor. Thus, especially in city traffic, i.e., in highly populated areas, the emission of waste gases and harmful substances is avoided.
The purpose of the addition of an internal combustion engine is to increase the radius of action of the vehicle, because, for example, an overhead trolley system is built only in the central area of the city, and therefore, in the outskirts of the city or on branch lines (detours) another drive aggregate is required.
On the other hand, such internal combustion engines can be used as a second drive aggregate in order to drive the vehicle when breakdowns occur in the external electrical supply network so that the operation of the vehicle can be maintained without disturbance.
In conventional buses (city buses as well as country buses), a number of additional auxiliary aggregates are required, for example, a water pump, an air compressor, and a power-steering pump for power steering. The auxiliary aggregates are driven by the internal combustion engine through one or more V-belts. The internal combustion engines of such conventional buses are designed for this additional power output and the required space for these auxiliary aggregates is available in the vehicle.
However, in trolley buses, such a direct drive of the auxiliary aggregates by the internal combustion engine is usually not possible. The problem arises that the auxiliary aggregates that are connected to the internal combustion engine are no longer driven when, for example in city operation, the drive is performed exclusively electrically, i.e., by the external electrical power supply via the electrical drive motor.
In combined drive devices of the type described herein, therefore, a separate dc on-board system has been installed, for example, with 24 volt dc voltage on the board of a trolley bus, this on-board system being connectable to the external electrical power supply through suitable transformers. Then a number of separate electric motors are connected to this on-board system, each of which drives an auxiliary aggregate. If the driving of the vehicle is performed via the internal combustion engine, for example, if there is trouble in the external electrical power supply, the internal combustion engine also drives an emergency power supply which supplies the on-board system with electrical energy.
It appears that such a design of a drive device with a plurality of parallel and separate auxiliary aggregates, each with their own electric motor and corresponding controls is very expensive and complicated and, moreover, requires significant space. Apart from the considerable cost that arises from the plurality of electric motors and controls, another disadvantage of such a design is the poor degree of cooperation of the drive device arrangement with these additional electrical drive devices.